The present disclosure relates generally to a photolithography system and, more particularly, to a liquid immersion lithography system and process.
The semiconductor integrated circuit (IC) technology has experienced rapid progress including the continued minimization of feature size and maximization of packing density. The minimization of feature size relies on the improvement in photolithography and its ability to print smaller features. The minimum feature size in an optical lithography system may be determined in part by diffraction, which is related to the wavelength of light and the medium through which the light shines. Accordingly, one approach to reducing feature size and improving resolution is to use light with a shorter wavelength.
Another approach is to use a medium between the lens and the substrate other than air. Since the index of refraction of a medium (referred to as ‘n’) is larger than one, the wavelength in the medium is reduced by the factor of n. This may improve resolution. One such method of enhancing resolution using a non-air medium is referred to as immersion lithography. Commonly used immersion lithography adopts water as media.